Incandescent lamp.



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UNITED STATES,

Patented May 5, 1903.

PATENT OFFIQE.

JOHN W. HOWELL, OF NEWARK, NEW JERSEY, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

INCANDESCENT- LAMP.

SPECIFICATION forming part of Letters Patent No. 726,929, dated May 5, 1903.

Application filed April 29,1901. Serial No. 57,883. (No model.)

To all whom it may concern.-

Be it known that LJOHN W.HOWELL,a citi This invention relates to incandescent elec-; tric lamps, and is of particular importance in connection with lamps with treated filaments intended to be operated at about'two hundred and twenty volts and upward. There has been great difiiculty in producing a lamp 'of this kind heretofore, for the reason that a filament sufficiently long and thin to be economical could not be successfully handled in the treating and exhausting operations in the manufacture of the lamps.

By my invention I am enabled to produce a sixteen-candle power treated filament which may be operated at two hundred and forty volts with an energy consumption of 3.4 watts per candle.

count of its weakness with a length sufficient to cause a high-voltage drop, is distorted in the treating-bottle (a step in its manufacture to render it uniformly conductive) after the vegetable matter of which it is composed has been carbonized. A very thin filament is so weak at the high temperature to which it is brought in the treating-bottle that it is unable to sustain itself. The same trouble occurs in the lamp-bulb during the exhausting operation, and besides this there is a damage to the filament both during the treating process and at a certain stage of the exhausting process from leakage-currents. By means of my invention these difficulties are avoided. I proceed by forming the filament of a plurality of sections, or, in fact, by taking several independent filaments and subjecting them to the treating. process, by which they are rendered'of uniform conductivity, Thus each section is only a fraction of the entire length and maybe treated without danger of sagging. Two of these filaments are mounted in the same bulb and on the same supporting-stem and connected together in series by a cement joint and attached to a finewire of which the following is a specifica To provide a lamp of this kind requires a very thin filament, which on ac support sealed in the glass of the stem, the

outer ends of the conjoined filaments being connected to independent conductors which form the lamp-terminals. It is necessary to successful exhaustion that the three cement joints shouldbe equally heated, otherwise the gases and hydrocarbons will not be sufficiently expelled from all of them, and in order to effect this I reduce the loss of heat in the joint between the adjacent ends of the two filaments by making the support of finer wire than the leading-in wires, thereby bringing the joint to the same temperature as the others by reason of its decreased heat-dissipating capacity. Both filaments being connected to one point add their heat, and the decreased capacity to dispose of the heat -raises it to an equality with that at the other joints. In order to drive out the moisture which is trapped in the pores of the joints, I subject the filaments after being mounted on. the stem to a heating process before putting the lamps on the pumps. By this procedure damage to the filaments from the high potential during the exhausting and treating processes is avoided and a satisfactory highvoltage lamp is produced.

The several features of novelty will be hereinafter more particularly described and will be definitely indicated in the claims appended.to the specification.

In the accompanying drawing, which illustrates my invention, is shown a side elevation of a lamp embodying my improvements. As will be seen, it is composed of a multiple filament formed of twosections connected in series relation, the several parts of which are marked 1 and 2, respectively. The connected ends of the two sections are secured together by a cement joint of the usual character and to a wire 3, sealed into the "stemof the lamp. In order to reduce the loss of heat at this joint, the wirer3'is made .ofsmaller cross-section than the other twoiwires' sealed into the glass pillar which supports the filament, the degree of fineness, of cotirse,var.ying according to the nature of the metal used, and the two connected legs of the filament are joined to the same end of the thin-wire support at the same point, thereby making this joint as hot as those with the leading-in wires. In order to prevent cross connection or contact of the two sections of the filament under vibration, I anchor them at intermediate points by iron wires 6 7, mounted on the ends of glass posts 8 9, fused fast to the stem which supports the filament. The outer ends of the multiple filament are connected with terminals 4 5, leading through the stem in the usual manner.

With a high-voltage lamp of the class to .which this invention relates damage is liable to result to the filament from current leakage during exhaustion across the ingoing and outgoing ends of the filament or from arcs or discharges which tend to form at comparatively low voltages at the pressures used in incandescent-lamp exhaustion. Besides this, a filament which is of sufficient tenuity to afford a voltage-drop of two hundred and twenty with sixteen-candle power will sag and become distorted. Both these difficulties are avoided by the construction hereinbel'ore described, the preliminary expulsion of the moisture and the equality of heating the joints permitting the exhausting operation to be conducted without damage to the filament.

WVhat I claim as new, and desire to secure by Letters Patent of the United States, is-

l. A highvoltage "incandescent electric lamp having a filament composed of a plurality of independent treated sections, the sections being joined near the stem on the end of a supporting-wire of smaller heat-radiating capacity than the terminals.

2. A high-voltage incandescent electric lamp having a filament composed of two independent treated sections connected near the stem hya joint of smaller heat-radiating capacity than the terminal joints.

3. A high voltage incandescent electric lamp having a filament composed of two independent treated sections connected by a cement joint supported on the stem, and means for insuring equality of heating of the several joints.

4. A high voltage incandescent electric lamp having a filament composed of two sections each of which is a treated filament, the two connecting at adjacent ends to the same point of a wire of smaller heat-dissipating capacity than the terminals and mounted in the stem, and an anchor for the intermediate points of the several sections.

5. A high voltage incandescent electric lamp containing two treated filaments connected in series relation and mounted at their junction on a supporting-wire of smallercrosssection than the supports for the terminals.

6. A high-voltage incandescent lamp having two independent treated filaments mounted on the same stem, connected in series relation, the point of connection being mounted on a support of smaller heat-dissipating capacity than the terminals, anchors for intermediate parts of the filaments, and glass supports mounted on the stem for said anchors.

In witness whereof I have hereunto set my hand this 25th day of April, 1901.

JOHN W. HOWELL.

Witnesses:

J 0s. D. FREDERICKS, JOHN E. MITCHELL, Jr. 

